1. Field of the Invention
This invention relates generally to the video display of information on a display apparatus. In particular, this invention relates to the manner in which information is initially entered and thereafter displayed on a communications terminal.
2. Description of the Prior Art
Information which is to appear on a video display of a communications terminal is often first stored in a memory within the terminal device itself. This stored information is sequentially accessed from the memory and subsequently displayed on a cathode ray tube commonly known as a CRT. The sequential accessing from memory and subsequent display of information on the CRT is usually accomplished at a sufficiently rapid rate so as to create the impression of a continuous image to the viewer. In this regard, the image usually appears as a number of distinct rows of characters arranged across the CRT.
In order to preserve continuity in the image thus being viewed, it is common practice to initially enter new information of the bottommost row of the video display. The previously-appearing rows of characters are simultaneously moved upwardly on the display so that the data previously appearing in the bottommost row reappears in the row next to the bottommost row. In this manner, each succeeding row reappears one row above its previous display position. This is commonly referred to as a "roll-over" of displayed information.
In order to internally facilitate the aforementioned roll-over of information, it has heretofore been a common practice to rearrange the rows of information within the memory portion of the display device. In this regard, the previous bottommost row is erased from that portion of memory dedicated to storing the bottommost row so as to allow for the subsequent storage of the new information that is to constitute the new bottommost row. At the same time, each of the other rows appearing above the previous bottommost row is erased from its particular memory location so as to accommodate the immediately preceding row. In this manner, the previous bottomost row is subsequently restored as the next-to-bottom row whereas the topmost row which had been previously displayed would be erased and no longer internally stored within memory.
It is to be appreciated that a considerable amount of time is thus expended in the reconfiguration of the internal memory during a roll-over of displayed information. It is furthermore to be appreciated that a considerable amount of logic must be dedicated to the task of reconfiguring the internal memory on a timely basis. Finally, it is to be appreciated that this logic must be operational for long periods of time when new information is sequentially being displayed on a display device.